The invention relates to utility meters, and more particularly to summing circuits used in such equipment to process metering signals.
Examples of prior compound flow meters are seen in Bradham III, et al., U.S. Pat. No. 4,100,799; Pelt, U.S. Pat. No. 4,217,929 and Kuhlmann et al., U.S. Pat. No. 4,429,571.
A compound flow meter incorporates a low volume flow meter and a high volume flow meter. The low volume flow meter is mechanically or magnetically coupled to a meter register to provide a readout of a volumetric consumption quantity. A high volume flow meter, often a turbine meter, is also coupled to a meter register, and may be coupled to the same meter register as the low volume flow meter. To determine total flow, the flows of the high volume flow meter and the low volume flow meter must be added together.
In the above-mentioned mechanical types of compound meters, as disclosed in Bradham III, et al., U.S. Pat. No. 4,100,799, a single register was mechanically coupled to both flow meters.
In Paz, U.S. Pat. No. 5,576,486, a compound flow meter is provided with an electronic module that performs the summation and outputs a result to a visual display. The electronic module is situated in a housing which is attached to the meter housing. In Paz, frequency signal inputs from the high volume flow and low volume flow are multiplied by respective multipliers K1 and K2, and the high volume flow signal is then multiplied by a ratio of K2/K1 to account for the difference in the two signals. The signals are then summed, multiplied by another multiplier K3, and then integrated to produce a volumetric consumption quantity which is output to a visual display.
A general object of the present invention is the retrofitting and interfacing of different types of existing meter registers to different types of meter data output devices. Thus, different input ratios may be present between signals from the high volume flow meter and the low volume flow meter. Different output ratios may be needed to operate different types of meter data output devices.
In addition, the summator unit must be small in size, low in cost, extremely versatile and suitable for harsh environments, such as subsurface pits for metering equipment. It must be easily connected to existing metering equipment.
The invention is practiced in a modular unit, which can be connected to various types of registers on compound meters, and which can be connected to various types of meter output devices and displays. The device is connected via convenient snap together connectors of the type disclosed in Karsten et al., U.S. Pat. No. 6,162,082, issued Dec. 19, 2000.
Inside the device, the steps of receiving and ratioing input data, summing the input data and ratioing the output signals are all performed. In addition, the circuitry provides for signal conversion for operation with a plurality of different meter registers and a plurality of different meter data output devices. Still further, the circuitry in the device provides for lead line (open circuit and short circuit) monitoring of a plurality of inputs, and logical summing of these results for passing through to the meter data output devices. Such a versatile interfacing device has heretofore been unknown in the industry.
The invention provides a method and apparatus in which the ratioing step can be easily switched between a ratio of 1:10 and 1:100 from the first input signal to the second input signal and from a ratio of 1:1 to 1:100 between the first input signal and the output signal.